1. Technical Field
The field of this invention is micro-fluidic devices.
2. Background of the Invention
Many important chemical processes are carried out in fluid environments, where such processes include chemical syntheses, fluid sample analyses, fluid component separations, and the like. In many situations, it is desirable to work with small volumes of fluid, e.g. from femtoliter to xcexcl quantities of fluid. Such situations include sample analysis in which small volumes of initial sample are analyzed; chemical synthesis, in which small quantities of chemical are desired and/or expensive reagents are employed, and the like. As such, there has been much interest in the development of micro-fluidic devices in which fluid is manipulated through one or more micro-channels present in the device.
A variety of different micro-fluidic devices have been developed in recent years. Such devices hold the promise of providing significant advantages over conventional macro-scale fluid manipulation devices. Such advantages include: ease of use, such that minimally trained technicians can operate the device; portability, such that fluid analyses can be conducted in the field as opposed to in the lab; reduced sample size requirements; reduction in solvent waste generation; and the like.
Despite the potential advantages provided by such devices, there are still significant technical obstacles that must be overcome if such devices are ever to realize their full potential. One such obstacle is the control of fluid flow, particularly between various regions or compartments in the device, i.e. control of fluid flow at the micro/micro interface level.
A number of purely mechanical approaches have been proposed in order to control the micro/micro interface in such devices. Purely mechanical means, e.g. valves, that have been proposed to control fluid flow in micro-fluidic devices include: flexible membranes, needle valves and the like. However, there are significant drawbacks associated with each of these proposals, which drawbacks include: inability to control the valve, lack of sufficiently strong materials, lack of ability to sufficiently seal the valve, etc.
As such, there is continued interest in the identification of a valve means for controlling fluid flow within a micro-fluidic device.
Relevant Literature
Micro-fluidic devices are described in U.S. Pat. Nos.: 5,770,029; 5,755,942; 5,746,901; 5,681,751; 5,658,413; 5,653,939; 5,653,859; 5,645,702;5, 605,662; 5,571,410; 5,543,838; 5,480,614, the disclosures of which are herein incorporated by reference.
Reversible gel compositions are described in U.S. Pat. Nos.: 5,720,717; 5,672,656; 5,631,337; 5,569,364; 5,670,480; 5,658,981; 5,470,445; 5,432,245; 5,298,260; 5,162,582; 4,439,966, the disclosures of which are herein incorporated by reference.
Micro-fluidic devices and methods for their use are provided. The subject devices are characterized by having at least one micro-valve that modulates fluid flow through the device. The micro-valve comprises a phase reversible material, e.g. gel, that is capable of reversibly changing its physical state in response to an applied stimulus. In using the subject devices, fluid flow is controlled by applying the appropriate stimulus to the micro-valve. The subject devices find use in a variety of different applications, particularly micro-fluidic analytical applications.